How can I change what the nodes are called in a function?

[idknuttin]

I wrote code that does what I want but I know I can make it shorter I just don't know why I can't change what the nodes I called inside of a function.

here is my code that works

  #include<iostream>

class ListNode{
public:
  int content;
  ListNode *pointerToNext;
};

void addElement(int input, ListNode** pHead){
  ListNode *temp;
  temp=new ListNode;
  temp->content=input;
  temp->pointerToNext=*pHead;
  *pHead=temp;
}

void deleteElements(int input, ListNode** pHead){
  for(int i=0; i>input; --i){
    ListNode *temp2;
    temp2=*pHead;
    temp2=temp2->pointerToNext;
    ListNode *temp3;
    temp3=*pHead;
    *pHead=temp2;
    delete temp3;
  }
}

int main(){
  std::cout<<"Insert a list of integers greater than or equal to -9";
  std::cout<<std::endl;
  std::cout<<"(inserting -9 will end the list)" <<std::endl;
  std::cout<<"inserting a negative number, z, will delete the last |z| numbers
              in your sequence." <<std::endl;
  int userInput;
  std::cin>>userInput;

  ListNode *head;
  head=new ListNode;
  head->content=userInput;
  head->pointerToNext=nullptr;

  while(userInput != -9){
    std::cin>>userInput;
    if(userInput >= 0){
      addElement(userInput, &head);
    }
    if(userInput < 0 && userInput > -9){
      deleteElements(userInput, &head);
    }
  }
  return 0;
}

I am trying to make the code a little better by replacing the void deleteElements(int input, ListNode** pHead) with this function

void deleteElements(int input, ListNode** pHead){
  for(int i=0; i>input; --i){
    ListNode *temp2;
    temp2=*pHead;
    *pHead=*pHead->pointerToNext;  //this is where I get compiler error
    delete temp2;
  }
}

1. I am trying to make head into the second node so that I can delete the first node, but I can't do *pHead=*pHead->pointerToNext;. Am I doing it wrong or is it impossible to do?

2. In my void deleteElements(int input, ListNode** pHead) function I tried to add delete temp; as the last line because each time the function is called it is creating another node called temp, so if the original temp isn't deleted does this cause a memory leak? When I try this the code compiles but I get a "segmentation fault (core dumped)" error.

[BAC Sun]

1. You should be able to use ++*pHead in order to move to the next pointer.

2. void deleteElements(int input, ListNode** pHead) doesn't have a member named temp. void addElement(int input, ListNode** pHead) does though. You can't really delete something that isn't there.

*pHead ends up pointing to the same location as temp after addElement so if you delete temp, you are effectively setting *pHead to NULL.

[idknuttin]

@BAC Sun, thank you, I was able to fix it. For my second question I meant to type void addElements, but I understand what you were saying.